Share-based Compensation - ESPP (Details) - Employee Stock Purchase Plan [Member] - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares reserved for future issuance, in shares	2.3		2.3
Purchase election as percentage of compensation	15.00%		15.00%
Purchase price as percentage of fair value			85.00%
Share-based compensation recognized cost	$ 0.1	$ 0.1	$ 0.3	$ 0.2

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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Purchase price of common stock expressed as a percentage of its fair value.

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